Sketching unit for transmission of sketches and notes over normal telephone lines

ABSTRACT

A sketching system sketches first notes to be transmitted over a telephone line and receives second notes from another sketching system. The sketching system includes a signal de-combiner device, receiving the second notes from the another sketching system and voice data as a combined signal via the telephone line and de-combining the combined signal into the second notes and the voice data. In addition, the sketching system includes a sketching unit connected to the signal de-combiner. The sketching unit includes a note displaying device displaying the first and second notes, a note generating device generating the first notes, and a processor connected to the note displaying and generating devices and to the signal de-combiner, receiving the first notes from the note generating device, receiving the second notes from the de-combiner, and transmitting the first and second notes to the note displaying device. The sketching unit further includes a clearing unit selectively clearing one of the note displaying device and another note displaying device of the another sketching system and an erase unit selectively erasing the first and second notes displayed on one of the note displaying device and the another note displaying device. Finally, the sketching system includes a first lock device selectively preventing the processor from transmitting the first notes to the signal de-combiner preventing the first notes from being displayed on the another sketching system, and a second lock device for selectively preventing the processor from transmitting the second notes to the note displaying device.

CROSS REFERENCE TO RELATED APPLICATION

This is a continuation of application Ser. No. 08/150,905, filed Nov.12, 1993, which is a continuation-in-part of application Ser. No.08/076,505 filed on Jun. 14, 1993.

FIELD OF THE INVENTION

This invention relates to the transmission of sketches and notes overnormal telephone lines, and more particularly, to a sketch pad unit foruse with a telephone for simultaneously transmitting voice analogsignals and sketch digital signals.

DESCRIPTION OF THE RELATED ART

It is often difficult to communicate directions, ideas and graphicalrelated concepts using a telephone in comparison to the ability toconvey this type of information in person by explaining the graphicalrelated concept using a drawing. For example, the ability to draw a mapfor providing travel directions is likely to save time and energyinstead of describing the directions in words over the telephone andhaving the person receiving the verbal directions draw the map from theverbal description.

Some sketch pads are available which generally transmit the graphicaldata over a telephone line in a manner which is unsuitable for use inconjunction with a telephone. For example, various delays in thetransmitting and receiving of the graphical data to sketch units areencountered during a voice communication. In addition, the userinterface for the sketch user is unsuitable for use for two sketch userscommunicating with each other from opposite ends of a telephone line.

Examples of prior an transmission techniques which have encounteredsignificant delays when analog voice and digital data is transmittedsimultaneously over a channel is typically either frequency-divisionmultiplexing or time-division multiplexing. In frequency-divisionmultiplexing, the data channel and the voice channel are allocateddifferent sub-bands of the channel's bandwidth. Examples of thesetechniques are U.S. Pat. No. 4,757,495, U.S. Pat. No. 4,672,602, andPat. No. 4,546,212. In time-division multiplexing arrangements, voicesignals are sampled, digitized and interleaved with digital data to forma single information stream which is communicated over the availablechannel. Practically every digital carrier system (e.g. the T1 carriersystem) is an example of time-division multiplexing.

U.S. Pat. No. 4,512,013, issued Apr. 16, 1985, presents an interestingapproach that is close to a frequency division multiplexing arrangementfor simultaneous voice and data transmission. The arrangement filtersthe speech signal and adds thereto a modulated narrowband signal to formthe transmitted signal. The narrowband modulated signal derives from anarrowband digital input signal that is modulated with a carrier,thereby shifting the narrow-band up in frequency to a position in thespectrum where there is little speech energy. At the receiver, inreliance of the fact that the speech power is low in the narrowbandoccupied by the modulated digital signal, the digital signal isrecovered through appropriate demodulation. Thereafter, the recovereddigital signal is demodulated to replicate the transmitter's operation,adaptively filtered to account for channel characteristics, andsubtracted from the received signal. The result is the received speech.As indicated above, one salient characteristic of that arrangement, asstated in col. 2, lines 13-18, is that" . . . an entire analog speechsignal and a modulated data signal are capable of being transmitted overa normal analog channel by the multiplexing of the data signal withinthe portion of the normal analog speech signal frequency band where thespeech signal is present and the power density characteristic thereof islow". As an aside, the U.S. Pat. No. 4,512,013 arrangement is halfduplex.

Additional techniques for transmitting digital data, e.g., data outputfrom the sketch unit, is found in the modem an where digital informationis communicated over a channel by converting the digital information toanalog form. In the most basic form, a modem filters the digital signal(i.e., shifts the signal in frequency) to form a band-limited signal andmodulates the signal to reside within the passband of the communicationchannel. In telephony, for example, that passband may be between 300 Hzand 3500 Hz. To increase the information-carrying capacity of themodulated signal, more sophisticated modems employ quadraturemodulation. Quadrature modulation is of ten depicted as atwo-dimensional signal space. Use of the signal space to send voiceinformation is disclosed in U.S. Pat. 5,081,647 issued Jan. 14, 1992.

Additionally, use of the signal space to send digital data, e.g., sketchdata, and analog data, e.g., voice data is described in "High SpeedDigital and Analog Parallel Transmission Technique Over Single TelephoneChannel", Ajashi et al., IEEE Transactions on Communications, Vol. 30,No. 5, May, 1982, pp. 1213-1218. Unlike prior techniques, where analogand digital signals were segregated into different time slots (TDM) ordifferent frequency bands (FDM), they describe separating analog anddata signals into the two different channels of the QAM system. That is,Ajashi et al. suggest modulating the in-phase channel with the analogsignal, and modulating the quadrature channel with the digital signal.Building on that description and concerning themselves with channelequalization, Lim et al. analyzes equalizer performance in "AdaptiveEqualization and Phase Tracking For Simultaneous Analog/Digital DataTransmission", BSTJ, Vol. 60 No. 9, November 1981, pp. 2039-2063. The1981 BSTJ article cites the information of 1982 IEEE article as"unpublished work").

However, currently, there does not exist a suitable user interface whichpermits a sketch user to effectively communicate graphical data withanother sketch user. In addition, there does not exist a suitable methodfor simultaneously transmitting voice and sketch data over a normaltelephone line so that the sketch users may cream and modify graphicaldata in an acceptable manner. More specifically, no one has achieved theability to simultaneously sent both digital and analog, signals (e.g.,sketch and voice data) through both channels of a QAM system, and no onehas achieved the ability to communicate both by data and analog,simultaneously, and in full-duplex, over a single hi-directional bandlimited communications channel.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide asketch unit which includes a user interface which is friendly andpermits users of the sketch unit to communicate with each other in anefficient and timely manner.

In addition, it is another object of the present invention to eliminatethe delay encountered when transmitting voice and sketch data over atelephone line.

Further, it is an object of the present invention to implement thetransmission of analog and digital information, simultaneously, and infull-duplex, over a single bi-directional band limited communicationschannel.

These and other objects of the present invention are accomplished byproviding a sketching system that sketches first notes to be transmittedover a telephone line during a telephone call using the telephone line,and the sketching system receives second notes from another sketchingsystem. The sketching system includes a sketching unit having a notegenerating device for generating the first notes. The sketching systemalso includes a signal de-combiner device, receiving the second notesfrom the another sketching system and voice data as a combined signalvia the telephone line and de-combining the combined signal into thesecond notes and the voice data. The sketching unit is connected to thesignal de-combiner. The sketching unit includes a note displaying devicedisplaying the first and second notes, the note generating devicegenerating the first notes, and a processor connected to the notedisplaying and generating devices and to the signal de-combiner,receiving the first notes from the note generating device, receiving thesecond notes from the signal de-combiner, and transmitting the first andsecond notes to the note displaying device. The sketching unit furtherincludes a clearing unit selectively clearing one of the note displayingdevice and another note displaying device of the another sketchingsystem and an erase unit selectively erasing the first and second notesdisplayed on one of the note displaying device and the nother notedisplaying device. Finally, the sketching system includes a first lockdevice selectively preventing the processor from transmitting the firstnotes to the signal de-combiner preventing the first notes from beingdisplayed on the another sketching system, and a second lock device forselectively preventing the processor from transmitting the second notesto the note displaying device.

Each sketching system preferably includes the ability to receivecombined voice analog data and digital data signals from other sketchingsystems and the ability to transmit the combined signal to othersketching systems.

According to another aspect of the sketching unit of the presentinvention, the de-combiner includes a de-modulator receiving thecombined signal and outputting a demodulated signal and a detectorreceiving the demodulated signal from the demodulator and for detectingdigital signal components included in the demodulated signal. Inaddition, the de-combiner includes a first de-mapper connected to thedetection means and generating the first notes responsive to the digitalsignal components, subtraction means for subtracting the digital signalcomponents received from the detection means generating component analogsignals and a second de-mapper connected to the subtraction means andgenerating the voice signal responsive to the component analog signals.

According to the simultaneous communication aspect of the presentinvention, analog information and digital information is communicationconcurrently when employing the principles of this invention. In generalterms, when the communication channel is viewed as a multi-dimensionalspace, the digital signal is divided into symbols, and the symbols aremapped into the signal space with a present distance between them. Theanalog signal, generally limited in magnitude to less than half thedistance separating the symbols, is convened to component signals andadded (i.e., vector addition) to the symbols. The sum signal is thentransmitted to the receiver where the symbols are detected andsubtracted from the received signal to yield the analog signalcomponents. The transmitted analog signal is recreated from thosecomponents.

In one illustrative embodiment for the simultaneous transmission ofdigital and analog data, the digital stream entering the transmittersection is divided into words, and each word is mapped to a pair ofsymbol components. The analog signal entering the transmitter section issampled and each pair of successive samples forms a set of analog vectorcomponents. The analog vector components are added, respectively, to thesymbol components and the component sums are QAM modulated to form theoutput signal. The pairs of analog samples can be derived by simplydelaying the analog signal and sampling both the delayed and theundelayed versions.

At the receiver, the signal is first demodulated and the digital signalis detected in accord with standard modulation technology. The detecteddigital signal is then subtracted from the received signal to formanalog sample pairs that are combined to reconstitute the analog signal.

Line equalization, echo-canceling, pre-emphasis, and other improvementsthat are known in the modem art can be incorporated in variousembodiments that employ the principles of this invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 presents the basic structure of a prior art modem;

FIG. 2 shows the signal space and an illustrative signal constellationfor the FIG. 1 system;

FIG. 3 shows the signal space of a QAM analog system;

FIG. 4 shows the signal space of an alternating digital and analogsystem;

FIG. 5 shows the signal space of a combined digital and analog system;

FIG. 6 presents one embodiment of a transmitter section for a combineddigital and analog system;

FIG. 7 depicts the vector addition that forms the signal space of FIG.5;

FIG. 8 presents one orthogonal modulation approach;

FIG. 9 illustrates the arrangements that permit more than one analogsignal source to be transmitted simultaneously;

FIG. 10 details the major elements in a receiver responsive to the FIG.5 signal space;

FIG. 11 presents a block diagram of a receiver that includes adaptiveequalization;

FIG. 12 presents the block diagram of an entire modem;

FIG. 13 presents a slightly different embodiment of the FIG. 12 mode;

FIG. 14 depicts one structure for scrambling analog samples;

FIG. 15 presents a block diagram of a privacy scrambler employingpseudo-random multiplication of the analog samples;

FIG. 16 illustrates a processor 75 being interposed between the analoginput and the analog port of the modem, with the processor being adaptedto carry out signal preprocessing functions, such as linear predictivecoding;

FIG. 17 presents a block diagram illustrating linear predictive coding;

FIG. 18 presents a block diagram illustrating the alternative use ofdifferent signal spaces;

FIG. 19 depicts use of the disclosed modem in connection with softwaresupport;

FIG. 20 depicts use of the disclosed modem in connection with apparatusdiagnosis and maintenance;

FIG. 21 depicts use of the disclosed modem in connection with apparatusdiagnosis and maintenance with the modem coupled to a wireless basestation;

FIG. 22 shows use of the disclosed modem in connection with a callcenter;

FIG. 23 shows use of the disclosed modem in an interactive gameenvironment;

FIG. 24 presents a block diagram depicting use of the disclosed modem inan interactive mode with a television display;

FIG. 25 presents the disclosed modem in a PCMCIA configuration, adaptedfor inclusion with wireless apparatus, such as a wireless computer;

FIG. 26 shows use of the disclosed modem in a telephone instrument thatincludes video capabilities;

FIG. 27 shows use of the disclosed modem in a fax machine;

FIG. 28 shows use of the disclosed modem in a personal computer;

FIG. 29 shows use of the disclosed modem in a "plain old" telephone; and

FIG. 30 presents a block diagram that includes the disclosed modem andmeans for bypassing the modem when it is inoperative;

FIG. 31 is block diagram of the conceptual structure of the sketchingunit of the present invention;

FIG. 32 is a block diagram of the construction of the sketching unit ofthe present invention; and

FIG. 33 is a diagram of the user interface of the sketching unit of thepresent invention.

DETAILED DESCRIPTION

To place this disclosure in context, FIG. 1 presents a very basic blockdiagram of a modem that communicates digital data via quadraturemodulation techniques. Section 100 is the modem's transmitter sectionand section 200 is the modem's receiver section. Specifically, in thetransmitter section digital data is applied in FIG. 1 to a 1-to-2 mapper110, and mapper 110 develops two outputs which typically are referred toas the in-phase and quadrature samples. The in-phase samples are appliedvia low pass filter 150 to modulator 120, which multiplies the appliedsignal by a carrier--i.e., sin ωt in FIG. 1. The quadrature samples areapplied via low pass filter 160 to modulator 130, which multiplies theapplied signal by a second carrier. The second carrier is orthogonal tothe first carrier; namely, cost ωt . Filters 150 and 160 must bebandlimited to no more than ω, in order to avoid aliasing and to atleast half the inverse of the output sample rate of mapper 110. Theoutput signals of modulations 120 and 130 are added in element 140 todevelop the analog signal of the modem's transmitter section.

In operation, the digital data applied to the FIG. 1 apparatus is astream of bits. Element 110 views the incoming signal as a stream ofsymbols that each comprises a preselected number of consecutive bits,and maps each symbol into an in-phase analog sample and a quadratureanalog sample.

Practitioners in the art often describe the operations performed in theFIG. 1 apparatus by means of a signal space diagram, such as shown inFIG. 2. The x axis corresponds to one of the carrier signals (e.g. cosωt) and the y axis corresponds to the other carrier signal (sin ωt). Thein-phase and quadrature samples delivered by element 110, in effect,specify a location in the signal space of FIG. 2. Accordingly, the setof possible samples that element 110 can produce corresponds to a set ofsample points (i.e., a constellation of points) in the signal spacedepiction of FIG. 2. A 4-point signal constellation is shown, by way ofillustration, in FIG. 2. It is well known, however, that one can createsignal point constellations with a larger number of signal points.

To receive signals that were modulated by the FIG. 1 apparatus inaccordance with the specific constellation depicted in FIG. 2, one mustonly identify whether the received signal is in the first, second, thirdor fourth quadrant of the signal space. That means that there existsgreat latitude in the signals that are received, and any received signalthat is still in the correct quadrant is mapped to the correctconstellation signal point in that quadrant. Extended to other (andperhaps larger) constellations, the signal space can be divided intoregions and the receiver's decision is made with respect to the regionin which the received signal is located. We call these regions"neighborhood" regions.

Returning to FIG. 1 and addressing the modem's receiver section, themodulated signal is applied to demodulated 210. Demodulator 210 recoversthe in-phase and quadrature components and applies them to slicer 220.Slicer 220 converts the in-phase and quadrature components into symbolsand applies the symbols to demapper 230. De-mapper 230 maps the symbolsinto bit streams to form the recovered digital data stream.

Absent any signal degradation (such as due to noise added in thechannel) the signal received by demodulated 210 would be precisely thesame as the signal sent by adder 140, and a determination ofneighborhood regions in which the signal is found (by slicer 220) wouldbe relatively simple and error-free. However, noise that is added to thetransmitted signal shifts the received signal in the signal space andmodifies the input to slicer 220. Stated in other words, a noise signalthat adds to the signal flowing through the communication channelcorresponds to a vector signal in the signal space of FIG. 2 that isadded to a transmitted sample point. The added vector is of unknownmagnitude and unknown phase. Consequently, added noise converts atransmitted signal that corresponds to a point in the signal space intoa region in the signal space. This phenomenon is depicted in FIG. 2 bycircle 11. Some refer to this circle as a signal space "noise cloud"surrounding the transmitted signal.

From the above it is clear that in order to detect the transmittedsignals without errors, the neighborhood regions must be large enough toencompass the noise cloud. Since the average power of the sent signal istypically limited by other considerations, the extent to which thesignal constellation covers the infinite space represented by the x andy axes is also limited. This is represented in FIG. 2 by circle 12. Therestriction imposed by circle 12, coupled with the restriction on thesize of the neighborhood regions that is imposed by noise considerationslimits the number of transmitted signal points in the constellation.

As indicated above, it has been observed that in typical modem designsthe allowable signal power and the expected fidelity of the channelcombine to control the constellation size. Less noisy channels allow forlarger constellations, and larger constellations permit higher digitaldata throughput.

The present invention utilizes a revolutionary method of transmittingand receiving data which directly contrasts with the previouslymentioned prior art method. Specifically, the present invention utilizesall or essentially all, of the available signal space for thetransmission of information. A transmitter signal space in accordancewith this revolutionary approach is depicted in FIG. 3 where a pluralityof signal points are depicted randomly within the signal space. Thesepoints are illustrative of the various vectors that the transmitter isallowed to send out. There are no more "constellations of points", wherea decision must be made between constellation points; there is only theentirety of the signal space. In other words, rather than having digitalsignals that are mapped onto a fixed constellations within a signalspace, FIG. 3 depicts analog symbols that are mapped onto a signalspace. When the analog signals that form the in-phase component areindependent of the analog signals that form that quadrature component,the viable signal space of FIG. 3 may be rectangular.

Having recognized the advantages of sending analog signals in accordancewith the signal space of FIG. 3, the next innovation is to alternatebetween the signal spaces of FIG. 2 and FIG. 3. That is, the innovationis to send the customer analog signals or the customer digital signalsas the need arises. This is depicted in FIG. 4.

Further, having recognized the advantages of sending either analog ordigital signals in accordance with the signal spaces of FIG. 4, it wasdiscovered that a totally different communication approach can be taken,that communicating both analog and digital signals, can be expressedconcurrently, in a combined signal space. This is illustrated in FIG. 5,where four neighborhoods are identified for illustrative purposes, withdemarcation borders identified by dashed lines 21 and 22.

According to the FIG. 5 depiction, the analog signals that form "signalclouds" around each digital constellation point (e.g., point 31) shouldbe restricted in their dynamic range to be totally contained within theneighborhood regions. Hence, here too there is a trade-off betweenconstellation size (which directly affects digital through-put) anddynamic range of the transmitted analog signal (which is some situationstranslates to "resolution").

FIG. 6 depicts an arrangement that very basically illustrates theprinciples disclosed herein. It includes a 1-to-2 dimensional mapper 60responsive to digital signals applied on line 61. Mapper 60 develops twooutput signals on lines 62 and 63, each of which possesses pulses withquantized amplitudes that relate to the digital signals arriving on line61. FIG. 6 also includes a 1-to-2 mapper 50 that responds to an appliedanalog signal on line 51, and it develops two output signals on lines 52and 53, each of which possesses pulses with continuous amplitudes thatrelate to the analog signal on line 5. Outputs 52 and 62 are combined inadder 70 and outputs 53 and 63 are combined in adder 80. The outputs ofadders 70 and 80 form the components of the signals that are representedby the signal space of FIG. 5. As in FIG. 1, the outputs of adders 70and 80 are applied via low pass filters 150 and 160 to modulators 120and 130 and summed in adder 140 to form a modulated signal as istypically known in the modem art.

In FIG. 6 element 60 is depicted as a 1-to-2 mapper. However, it shouldbe understood that element 60 can be an M-to-N mapper. That is, element60 can be responsive to a plurality (M) of digital signals and it candevelop a different plurality (N) of output signals. Similarly, element50 can be a J-to-K encoder that is responsive to a plurality of analogsignals. Likewise, the collection of elements that follow elements 50and 60 (i.e., elements 70, 80, 120, 130, 140, 150 and 160), which formorthogonal modulator 90 can be constructed to be responsive to whateverplurality of outputs that elements 50 and 60 are designed to produce(e.g., three dimensional space, four dimensional space, etc.). Morespecifically, those elements must account for all of the applied inputsignals, and that means that they must be able to handle K or N signals,whichever is larger. In such a circumstance, however, the user canassume that the larger of the two (K or N) is the dimensionality of thesystem, and some of the dimensions have either no digital data, or noanalog data, whichever applies. Of course, if there are "dimensions" forwhich there is no digital or analog data, other information can be sentover those dimensions, such as equalization "side" information.

In the context of a signal space, the N pluralities of output signals ofelements 50 and 60 (assuming N is larger than K) correspond to thecollection of components of vectors in multi-dimensional space; e.g.,N-dimensional space. The coordinates of this multi-dimensional spacecorrespond to the orthogonal modulation signals within orthogonalmodulator 90. IN FIG. 6, the two orthogonal modulation signals are cosωt and sin ωt, but other modulation signals are also possible; forexample, code division multiplexing (CDMA) templates. For purposes ofthis disclosure, orthogonal modulation signals are modulation signalsthat develop a transmitted signal comprising concurrent element signalsand yet allow the receiver to separate the received signal into itsconstituent element signals, those being the signals developed inresponse to each of the modulation signals. It may also be observedthat, relative to FIG. 5, orthogonal modulator 90 performs vectorsummation of the symbol vector represented by the components developedby element 60 with the analog information vector represented by thecomponents developed by element 50. This is depicted in FIG. 7.

In connection with FIG. 1, it may be noted that the principles disclosedherein may be utilized even when the output signals of adders 70 and 80are communicated (e.g., transmitted) directly, without the benefit ofcombining them in orthogonal modulator 90. Also, orthogonal modulator 90can simply be a bandshifting means. To the extent that the output ofadder 70 (for example) is bandlimited, the output of adder 80 can beshifted beyond the band-limited output signal of adder 70 and combinedwith the output signal of adder 70. This is presented in FIG. 8. It mayalso be appreciated that the principles disclosed herein may beexercised without the use of element 60 in those situations where nodigital streams are presented.

To this point in the instant disclosure, the implication has been thatthe input signal applied to element 50 of FIG. 6 is analog. However,that does not have to be strictly the case. In accordance withconventional techniques, an analog signal that is bandlimited can besampled (within the proper Nyquist bounds). Hence, it should beunderstood that the input signal to element 50 can be a sequence ofanalog samples. Moreover, a sampled analog signal can be quantized andrepresented in digital form. Indeed, an analog signal that has beensampled and converted to digital form can then be converted to amplitudequantized pulse amplitude-modulated format; e.g., conventional PCM. Allof those representations are representations of an analog signal. Forexample, the collection of the amplitude-quantized PAM pulses isidentical to the original analog signal within the bounds of thequantization errors introduced by the sampling and quantizing (A/Dconversion followed by D/A conversion) processes.

The fact that sampling and amplitude quantization of the analog signalat the input of element 50 is permitted offers a number of benefits. Forone, it allows the signal to be presented to element 50 in digitalformat. For another, it permits simple multiplexing of differentinformation sources. Thus, for example, elements 50, 60 and 90 can beimplemented in accordance with present day modem realizations; i.e.,with one or more microprocessors operating under stored program control.

An example of input signal multiplexing is shown in FIG. 9, whichpresents an embodiment that includes an A/D converter bank 30 followedby a multiplexer 40. Converter bank 30 converts a plurality of analogsignals, such as on lines 33 and 34, to digital format and multiplexer40 multiplexes its input signals and applies them to element 50.Elements 30 and 40 are conventional A/D and multiplexer elements,respectively.

The combination of elements 30 and 40 allows applying a number ofnarrowband analog signals to orthogonal modulator 90. The primarylimitations are the carrier frequency and the allowable transmissionbandwidth of the channel. The narrowband signal can, of course, comefrom any source. For example, a system installed in an ambulance maysacrifice some voice bandwidth in order to allow narrowband telemetrydata of blood pressure and heart pulse rate to be communicatedconcurrently with the voice.

Additionally, a voice signal energy detector may be included, such asdisclosed in U.S. Pat. No. 5,081,647, which would detect periods ofsilence and send less urgent telemetry data during those silenceperiods. The silence periods may be naturally occurring periods, orsilence periods enforced for the purpose of communicating telemetryinformation, such as data about the analog information just sent orabout to be sent. This is illustrated by elements 31 and 32 in FIG. 9.

The fact that the input to element 50 is digital (in a digitalimplementation of elements 50, 60 and 90) and that the input to element60 is also digital should not be confused. The digital input to element60 is a stream of digits that are each equally important. Hence, thosedigits are converted into symbols and the symbols into constellationpoints, and the constellation points are within neighborhoods which areidentified by a slicer (e.g., slicer 220 in FIG. 1) within a modem'sreceiver section. In contradistinction, the digital signals applied toelement 50 correspond to digital words that represent amplitude, and thespecific interrelationship between adjacent bits of the digital words ismaintained. As indicated above, being a fundamental distinction, thesignal cloud around a signal point within a constellation does notrepresent a plurality of signal points that must be distinguished.

FIG. 10 represents a basic block diagram of a modem's receiver sectionin conformance with the principles disclosed herein. The modulated inputsignal received from the channel is applied to demodulator 210 whichdevelops the in-phase and quadrature components. Those are applied toslicer 220 which identifies the symbols, and the symbols are applied tode-mapper 230. All this is in accord with conventional modem approaches,as described in connection with FIG. 1. In addition, FIG. 10 includes amapper 240 that is responsive to the symbols developed by slicer 220.The output of mapper 240 is an accurate estimate of the set of in-phaseand quadrature components (that are applied in the FIG. 1 arrangement toelements 150 and 160). The outputs of mapper 240 are subtracted from theoutput of demodulated 210 in subtractors 250 and 260. The outputs ofsubtractors 250 and 260 are applied to 2-to-1 de-mapper 270 whichrecombines the analog samples to form an estimate of the original analogsignal. De-mapper 270 performs the inverse function of mapper 50.

It may be noted that slicer 220 can be designed to directly provide theoutput signals that mapper 240 develops; and moreover, de-mapper 230 canbe made responsive to such signals. That would alter the FIG. 10 in thesense that slicer 220 and mapper 240 would combine to form a singleelement and de-mapper 230 as well as adders 250 and 260 would beresponsive to that combined element.

In analog realizations (e.g., FIG. 6), mapper 50 is responsive to analogsignals. Various approaches can be taken to develop the plurality ofoutputs (two outputs, in the case of element 50 shown in the FIGS.). Forexample, a single bandlimited analog signal can be divided into aplurality of baseband signals by simply filtering and modulatingselected sub-bands. Alternatively, element 50 can accept a plurality ofbandlimited analog signals and assign each of the plurality ofbandlimited analog signals to different outputs of element 50.

In time sampled realizations (whether the realization continues withanalog circuitry or digital circuitry), element 50 can simply routealternate samples of a single analog signal to different outputs ofelement 50, or multiplex a plurality of analog signals and distributethe samples of those signals in any convenient manner.

In order to allow for nonlinear techniques that may be employed toenhance the communication qualities, it is important to effectequalization of the channel in order to minimize intersymbolinterference. Conventional modem technology can be brought to bear tothis need.

FIG. 11 presents a block diagram of an arrangement that incorporatesequalization. Specifically, FIG. 11 is depicted with a modulator that isfollowed by equalization hardware (which together can be thought of as asuper-demodulator). The equalization hardware comprises an adaptivefilter 280 that is interposed between demodulated 210 and slicer 220.The operational characteristics of filter 280 are controlled by filtercoefficients that are stored--in modifiable form--within tap updateblock 290. Tap update block 290 is responsive to the output signals ofsubtractors 250 and 260. The adaption of filter 280 is carried out inaccordance with conventional modem techniques. The outputs ofsubtractors 250 and 260 are also applied to demultiplexer 275 and theoutputs of demultiplexer 275 are applied to demapper 276. De-mapper 276comprises a bank of de-mappers 270 of FIG. 10. Elements 275 and 276 areincluded to illustrate a receiver that is adapted for applications wherea plurality of analog inputs are multiplexed. Of course, in applicationswhere there is no multiplexing, de-mapper 270 can be substituted.

In accordance with some adaptation approaches, it is easiest to carryout adaptation and the corresponding coefficient updates when the powerin the analog signal is small. To limit the process to such intervals,FIG. 11 includes a power detector within control element 295 that isresponsive to subtractors 250 and 260. Block 295 is also conventional.It includes a power detection circuit that evaluates the power containedin the signals of subtractors 250 and 260 and delivers a control signalto block 290 to enable (or disable) the coefficient updating process. Ofcourse, block 295 may be more generic, in that the control signal can bederived from other than the analog signal, such as from side informationfrom the transmitter.

FIG. 11 depicts one arrangement for effecting equalization of thetransmission channel between a sending modem's transmitter section and areceiving modem's receiver section; to wit, at the receiver's front end,following the demodulator. However, it is well known that equalizationcan be performed anywhere along the channel, going back even to within amodem's transmitter section.

FIG. 12 depicts the entire, full duplex, modem constructed in accordancewith the depictions of FIGS. 9 and 11. More specifically, a transmittersection (FIG. 9) is coupled with a receiver section (FIG. 11) throughhybrid 300 and subtractor 310. Subtractor 310 cooperates with echocanceler 320 in the conventional way to subtract unwanted signals fromthe signal applied to demodulator 210. For sake of simplicity, echocanceler 320 is shown connected to the output of orthogonal modulator90, and in analog embodiments of element 320 this is perfectlysatisfactory. However, in digital embodiments it is well known thatefficiencies can be realized by having the echo canceler be responsiveto the outputs of mapper 60, where the signal rate is much lower.

An improvement which incorporates the principles disclosed herein isshown in FIG. 13. It may be noted that some of the elements in FIG. 13are designated by different labels; such as "Hilbert passband filter",which corresponds to a modulator, etc. These are circuits that attainthe desired results through somewhat different calculations and are wellknown to persons skilled in the modem art.

The echo canceling is performed, as in all modems, during a trainingperiod, when the far end signal source is silent and the echo canceleris adapted to minimize the output of subtractor 310.

In connection with FIG. 6 it has been disclosed that the input toelement 50 can be a sampled analog signal, as well as an unsampledanalog signal. It has also been disclosed above that when element 50 isa 1-to-2 mapper (as compared to 1-to-N mapper) and the desired output ofelement 50 is pairs of a sampled analog signal, the pairs of analogsamples can be derived by simply delaying the incoming analog signal by1/B and sampling both the delayed and the undelayed versions at rate B.This provides sample pairs that correspond to adjacent samples of theoriginal analog signal sampled at rate 1/2 B seconds. Actually, privacyof the communication is enhanced when the samples are not adjacent, andFIG. 14 presents one approach for deriving pairs from non-adjacentsamples. It basically includes an input register 55 for storing K analogsamples that arrive at rate 2B, a scrambling network 56 that scramblesthe outputs of register 55 and develops K outputs, and registers 57 and58 that are responsive to the outputs of network 56. Registers 57 and 58store K/2 analog samples every K/2B seconds and output the storedsamples at rate 1/2 B seconds. Scrambling network 56 may be simply across-connect field.

Another approach for enhancing privacy entails modifying the gain andphase of the analog signals that are sent. This is akin to operating on,or transforming, the signal components that form the signal vector whichis added to the constellation symbols. The transforming may be inaccordance with the signal characteristics, or it may simply befollowing a pseudo-random sequence. The latter is depicted in FIG. 15,where register 72 receives analog signal sample pairs and directs eachmember of a pair to a different multiplier (73 and 74). Multipliers 73and 74 modify the applied signal samples in accordance withcorresponding coefficients that are received from pseudo-randomgenerator 71, resulting in a pair of modified signal samples that areapplied to mapper 50. Additional teachings of this technique are foundin the U.S. Pat. No. 4,924,516, issued May 8, 1990, to G. Bremer and W.Betts.

Of course, the receiver ought to include a pseudo-random generator thatis synchronized to generator 71 in order to properly decode the analogsignal. The FIG. 15 circuit can be incorporated in a receiver (such asthe FIG. 11 receiver) within to the de-mapper that develops the analogsignal. Synchronization of the FIG. 15 circuit in the receiver isachieved via synchronization information that is sent by the transmitteras "side information".

Characterizing the enhancement more generally, modifying the inputsignal based on the input signal's characteristics is a generalenhancement of the embodiments disclosed herein. The signal's amplitude,for example, can be dynamically modified to enhance the attainablesignal to noise ratio. The dynamic scaling of the signal can becommunicated to the receiver in the form of "side information" either onthe digital channel, or on the analog channel (for example, via one ofthe channels described in connection with the FIG. 9 embodiment). Thisis depicted in FIG. 16, where signal processor 75 precedes switch 32.Processor 75 modifies the signal applied to switch 32 and also providesthe aforementioned side information that is applied to A/D converterbank 30.

It may be noted in passing that some side information can also beincluded in the analog channel itself, by "stealing" some samples fromthe analog signal stream. Of course, with some realizations that wouldcreate missing samples at the receiver, but interpolation techniques atthe receiver can create close estimates of the missing samples.

Still another way to modify the signal is to control its dynamic rangethrough automatic gain control (AGC) which may be effected inconventional ways.

Yet another way to modify the signal is to encode it, and that includes,for example, the entire field of predictive encoding.

In predictive coding, the object is to predict the present signal frompast signals and to transmit only the error, or residue, signal, thatis, the signal that represents the deviation of the true signal from thepredicted signal. It is expected, of course, that with good predictionthe residue signal will be small. An arrangement that creates only smallresidue signals allows the residue signals to be amplified (in a fixedmanner or dynamically), achieving thereby good signal resolution andhigh noise immunity.

The residue signal sample, e(n), is typically developed by thecalculation:

    e(n)=x(n)-a.sub.1 x(n-1)-a.sub.2 x(n-2)-a.sub.3 x(n-3)

in response to input signal samples x(n), x(n-1), x(n-2), and forpreselected coefficients a₁, a₂, a₃, . . .

It may be noted that the number of coefficients is a designer's choice,and that the number of coefficients can also be a function of signalcharacteristics. For some signal characteristics the number ofcoefficients may be two, for others it may be three, etc. Also, thevalues of the coefficients may be fixed (and set in accordance withhistorical determinations) or variable, based on considerations such asshort term history of the signal, the current number of symbols in theconstellation, etc.

Processor 75 of FIG. 16 may be employed to perform the selectedencoding. More specifically, processor 75 may perform the function of alinear prediction coefficient generator that is sensitive to thecharacteristics of the input signal, and may also perform the functionof the augmentation filter. The coefficients developed by the linearpredictive coefficient generator portion of processor 75 delivers thecoefficients as side information to the A/D converter block, to betransmitted to the receiver and used therein in accordance with theequation

    y(n)=e(n)+a.sub.1 y(n-1)+a.sub.2 y(n-2)+a.sub.3 y(n-3) . . .

FIG.17 presents a block diagram of the transmitter and receiver portionsthat handle the linear predictive coding (elements 65-69). The blocksmarked "svd system" represent the receiver and transmitter portions ofthe modem embodiments (svd modem) disclosed above (e.g. FIG. 13).

Yet another way to enhance operation is to employ pre-emphasis. Forexample, the "analog" input that enters orthogonal modulator 90 can beentered to pre-emphasize the high frequencies and, correspondingly, the"analog" output of subtractors 250 and 260 can be filtered to remove thepre-emphasis. The pre-emphasis can be effected, for example, within theA/D converter 30 or even prior thereto, such as in pre-emphasis filter20 shown in FIG. 12. The filtering can be done while the "analog" signalis truly analog, or it could be done when the "analog" signal isrepresented digitally--such as when the transmitter and receiversections are implemented with digital hardware.

One aspect of the embodiments described above which employs a samplingprocess for the analog signal applied to mapper 50 is the limitation onthe highest frequency that may be included in the applied signal inaccordance with Nyquist's criteria. Stated in other words, regardless ofthe bandwidth offered by the communications network, a decision tosample the incoming signal at the symbol rate of mapper 60 places alimit on the upper frequency of the sampled signal. In someapplications, such as in speech applications, it may be desirable totransmit higher frequency signals even if the cost of achieving thecapability is a foregoing of some low frequencies.

This capability is realized by frequency shifting. That is, the speechsignal is bandlimited, a preselected portion of the low frequency bandis deleted, the resulting bandlimited signal is shifted downward, andthe shifted signal is sampled.

These operations can be performed with conventional filtering andmodulation circuitry or, alternatively, these operations can beperformed with Hilbert filters. At the receiver, this process isreversed, of course.

A number of implementations described above require transmission of"side information" to the receiver. Also, as described above, thisinformation can be sent on the analog channel or on the digital channel.

When the side information is sent on the digital data channel, it isembedded using DLE (Data Line Escape) shielding. More specifically, theside information is inserted in the data channel's bit stream while thatchannel's information is momentarily halted. In DLE shielding, the sideinformation is preceded by a specific bit sequence known as the "commandsequence", and may consist of either fixed-length bit stream or avariable-length bit stream followed by a termination sequence. Thecommand sequence indicates that the data to follow is side informationand not main channel data.

Since any sequence of bits chosen for the command sequence could alsoappear in the customer data bit stream, a safeguard method is used toensure the instances of the command sequence which do appear in customerdata are not interpreted as true command sequences. In the transmitter,at the same point in the system where side information is embedded inthe data stream, the input bit stream is monitored for instances of thecommand sequence in the customer data. At each point in the bit streamwhere an instance of the command sequence is detected, the transmitterinserts a duplicate sequence immediately following the original.

At the receiver, the input bit stream is again monitored for instancesof the command sequence. If a command sequence is detected, the bitstream immediately following is checked for a duplicate instance of thesame sequence. If such a duplicate is detected, indicating that theoriginal sequence is in the customer data and not a true command flag,the receiver deletes the duplicate sequence from the data stream andcontinues monitoring. If, however, no duplicate is detected, thesequence is a true control flag. The receiver removes both the commandsequence and the following side information from the main channel bitstream and routes the side information to its appropriate destination.

The method described above works regardless of how many instances of thecommand sequence are duplicated sequentially in the customer bit stream.Each instance is treated separately, with a duplicate instance insertedfollowing the original. At the receiver, each pair of instances istreated separately, with the second in the pair discarded. As a result,if an even number of instances of the command sequence is detectedfollowing each other in the receiver, the output will consist of onehalf of the number of instances in the customer clam stream and no sideinformation. If an odd number n of instances is detected, the outputwill consist of (n-1)/2 instances in the output data stream and routingof side information in the receiver which is indicated by the last(unduplicated) command sequence.

Having described a number of enhancements to the basic embodiments, itis clear that various novel combinations can be created to providevaried benefits. FIG. 18, for example, shows an arrangement wheredifferent signal spaces are employed at different times. The differentsignal spaces can be used at preselected times, or their use can beapplication dependent. The transmitter section of FIG. 18 includes atransmitter signal space selector switch 410, a data-only signal spacecoder 411, an analog-only signal space coder 412, an analog and datasignal space coder 413, and a dual-use signal coder 414.Correspondingly, the receiver section includes a receiver signal spaceselector switch 420, a data-only signal space decoder 421, ananalog-only signal space decoder 422, an analog & data signal spacedecoder 423, and a dual-use-signal space decoder 424.

The data-only coder 411 corresponds to the FIG. 6 coder with no input atline 51. The analog-only coder 412 corresponds to the FIG. 6 coder withno input at line 61. The analog & digital coder 413 corresponds to theFIG. 6 coder as described above, and the dual-use coder 414 is a coderwhere the symbols of line 61 in FIG. 6 are applied to only one of theorthogonal modulators, and the signals of line 51 in FIG. 6 are appliedonly to the other of the orthogonal modulators.

As indicated above, the signal space changes can be planned a priorisuch as at predetermined symbol times (e.g., with symbol counter 415 andselector 416). One might wish to send data only alternated with analogonly, with the timing ratio being completely an option of the user.Alternatively, one may signal the beginning of a specific signal spacemode, and signal again when that mode changes. The signal spaces neednot be the same in the two communication directions. All such signalingis effected through "hand shaking" protocols between the communicatingmodems; which in the example shown in FIG. 16, is merely asynchronization between TX Symbol counter 416 and RX Symbol Counter 426.

The issue of sending side information has generally been discussedabove, but it may be useful to also address a specific case of "sideinformation": establishing and dismantling a connection.

In applications where a conventional telephone is connected to theanalog port, the question is how will the connection be established anddismantle. FIG. 30 illustrates the arrangement for accomplishing thesetasks, with a controller 610 that is connected to a modem 600.

As disclosed above, most current modems implement the necessary functionin a processor that is under influence of stored program control. Thatis, the functions are implemented by programs that operate on numbersrepresenting signals and ultimately develop the called-for signals. Insuch realizations, controller 610 is arranged to interrupt the normalprogram flow in modem 600 whenever the right conditions occur.

Thus, when telephone 620 goes "off hook", controller 610 senses thecondition and forwards an interrupt to the microprocessor within modem600. Modem 600 then goes into a "control mode" which reads theinstructions provided to modem 600 by controller 610. When controller610 specifies an "off hook" condition, modem 600 is reconfigured to passthrough the signals arriving at the analog port directly to thetelephone network. This can be accomplished in modem 600 by providing aseparate signal path that is enabled, or by conditioning the variouselements in the signal path to achieve the same end results. Whentelephone 620 is thus connected, dial tones can then flow to thetelephone central office and establish a connection.

When a connection is established to a far end customer, modem 600 sendsa tone, identifying itself as a) a modem and b) an svd modem. Once aconnection to the far end equipment is established and the far endequipment identifies itself as an svd modem, then modem 600 assumes itssvd modem architecture. If the far end equipment identifies itself as annon-svd modem, then modem 600 can establish itself as a conventionalmodem connecting its digital port to the far end equipment. Lastly, ifthe far end equipment identifies itself as a conventional telephone,modem 600 remains in its "short circuited" mode.

Dismantling a connection is at least as easy. An "on hook" condition isdetected by controller 610 and, there is no "conversation" establishedon the data side, controller 610 signals modem 600 to turn itself off.

The "off hook" and "on hook" signaling described above is justillustrative. Other signaling can, of course, be used. For example, onthe analog side, controller 610 can be responsive to touch tonesequence, including the "#" and the "*" tones. On the digital side, theDLE shielding signaling can be employed. In this manner, once a digitalpath is maintained, the digital signal source can effect a "disconnect".

FIG. 30 also depicts an enhancement for a modem failure mode. Thisenhancement would advantageously be incorporated in all uses of thedisclosed modem where connection to a telephone function is desired evenin the absence of local power. Specifically, FIG. 30 includes a pair ofleads from the analog side of the modem to a pair of relay contacts 630.Relay contacts 630 are arranged to connect the telephone network leadsto the telephone network port of modem 600 when modem 600 isoperational, or to the analog port of modem 600, otherwise. The relaycoil that operates contacts 630 (not shown) may simply be responsive tothe leads that power modem 600, or to a "status OK" output lead of themodem.

In addition to the myriad combinations and permutations of capabilitiesthat are achievable with modems employing the principles disclosedherein, there are also many novel applications that can now be realize.The following are just a number of examples.

Remote Software Support

It is not uncommon for a purchaser of a software package to requireassistance from the software provider. Often it is beneficial for thesoftware provider to see exactly what is occurring at the user'scomputer terminal but, currently, the best that a support person at thesoftware provider's facility can do is attempt to duplicate the behaviorof the user's computer. This is not always successful. With a modememploying the principles disclosed herein, it is possible for thesoftware supplier to receive data from the customer's computer directly,in the same communications channel over which the customer and thesoftware supplier's support person converse. This is depicted in FIG.19.

Remote System Support

In addition to the capabilities described above in connection withsoftware support, one may desire to have support provided for thehardware. There are already many systems on the market where diagnosticscan be applied through electronic ports. Examples of that are PBX's,computers, car, etc. Many more such systems will be developed in thenear future. With a modem employing the principles of this invention, itis possible for a manufacturer to be connected to a malfunctioningapparatus at the customer's premises, and to test the apparatusremotely. In some cases, such as with computers and computerperipherals, remote repair can even be effected--e.g., by downloadingnew software. This is illustrated in FIG. 20.

In a home environment, it is likely that the equipment that may need tobe remotely diagnosed may need to be also accessed by the user while theuser is speaking with the manufacturer's support person. Since it isexpected that such devices may not always be in close proximity to thetelephone, customers will no doubt wish to employ their cordlesstelephones. To that end, it is beneficial to incorporate a modememploying the principles disclosed herein in the cordless telephone'sbase station. This is depicted in FIG. 21.

Home Agent

With increased sensitivity to environmental pollution that comes aboutfrom commuting to work, it is expected that many more people will beworking at home. An agent that is typically interacting betweencustomers who call in through an automatic call distributor (ACD) and acomputer is an ideal candidate for a "work at home" situation. A typicalexample of such an agent is an airline Reservations Agent. FIG. 22depicts such an arrangement employing a modem as disclosed above. Acustomer calls in to the Call Center and through the Call Center isconnected to the home agent over the analog channel. Concurrently, thehome agent is connected through the data channel to the computer in theCall Center. The home agent interacts simultaneously with both thecustomer and the Call Center's computer.

Of course, there is no requirement for the voice channel to be connectedto a customer outside the Call Center. Connection of the home agent toits home base location (via the Call Center or any other place ofbusiness) for both voice and data is achievable with the modem disclosedherein.

Home Entertainment

Presently, youngsters who wish to play electronic games must sittogether in one room and interact with the game device. With modems asdisclosed above, that is no longer necessary. A connection can be madebetween two homes, with the data channel devoted to communicatingbetween the two game devices, and the voice channel devoted to theconversation path between the two players. The bandwidth required forthe data channel need not be very large because it need only communicatecontrol information (such as start/stop and movement information) thatoriginates with the player and is applied to the game device.

As in connection with the cordless telephone's base station, the modemdisclosed herein is incorporated in the game device. This arrangement isdepicted in FIG. 23.

TV Interface

Currently, television sets receive their input from an antenna, or froma coax cable. Much like the cable connection, televisions can receiveinput from a filter cable--providing a much increased bandwidth--, aswell as from a conventional telephone tip-ring cord--providing a muchreduced bandwidth. Whatever the nature of the connecting cable,televisions connected to cables are becoming interactive. That is, thecable service providers provide a two directional channel path, throughwhich customers can actively interact with the cable service providers.

FIG. 24 depicts an embodiment which integrates telephony, datacommunication and video control for a conventional telephone cordconnection to a television. Of course, because of the very low bandwidthof the telephone cord, only sequences of still pictures can betransmitted to the television. In FIG. 24, element 430 is the modemdisclosed herein. It is connected to the telephone network via line 431.The analog port of modem 430 and the digital port of modem 430 areconnected to video card 440 via hybrids 432 and 433. Modem 430 receivesimage and voice signals from line 431, card 440 combines the receivedsignals, forms a composite signal and applies the composite signal totelevision 450.

Cordless telephone 460 communicates with line 431 through the cordlessbase station electronics 465. The arrangement of FIG. 24 contemplatesthat the voice signals would be applied to the telephone line throughhybrid 432 and modem 430. The touch tone signals, which are the controlsignals sent to the cable service provider are convened to digital formin block 434 and applied to the telephone line throughout hybrid 433 andmodem 430. Hybrids 432 and 433 merely ensure that the data sent to thetelephone line does not interfere with the information sent to thetelevision. 0f course, if the control signals can be embedded in thevoice signal and deciphered by the cable service provider at the distantend, then the connection between block 465 and the digital port of modem430 can be severed and elements 433 and 434 can be deleted.

The above-described arrangement that contemplates use of a telephonecable can be easily extended to wide bandwidth cables 431. All that isneeded is a frequency division splitter interposed between the cable andmodem 430. The high bandwidth signals that are destined to the TV can besent directly to the TV, while the low bandwidth communication channelis sent to modem 430.

The above-described arrangement can also be extended as described inmore detail hereinafter to recognize and react to control signalsarriving from base station 465. Such signals, e.g., "on-hook" and"off-hook" signals, can be recognized by controller 434 which isarranged to apply control signals to modem 430, causing modem 430 toreact to the control signals in the appropriate manner. In a modem 430implementation that includes a stored program controlled microprocessor,controller 434 can merely send an appropriate interrupt signal to thecontroller.

Cellular

Cellular telephony is extending to data. A number of companies are nowoffering arrangements where computers are connected to distant nodes viacellular networks. Some of these new computers are even so small thatthey are termed "notepad" computers. Data is sent by computers throughmodems, and modems now exist that are fully contained within a PCMCIAstandard card.

As depicted in FIG. 25, notepad computer 500 is adapted to receive aPCMCIA modem 510 that is constructed in accordance with the disclosureherein, and this modem includes a voice port 511. With the system ofFIG. 25, users of the computer can achieve the same connectivities thatusers of the previously described systems can achieve. Optionally, thePCMCIA modem also includes a conventional RJ-11 socket (512, 513) forplugging in a conventional telephone.

Of course, device 500 need not be a computer. It can merely comprise thewireless transmission and receiving circuitry that interacts with modem510, offering a digital port for whatever use may be desired. Forexample, a "wireless svd modem" can be placed on a dashboard of a carthat is being maintained, the digital port would be connected to theanalysis port of the car's electronic system, the analog port would beconnected to a telephone instrument and the car mechanic would then beable to converse with a service center in the manner described inconnection with FIGS. 19-21.

Enhanced Hardware

All kinds of hardware that are currently connected to the network canincorporate the modem disclosed herein. This includes fax machines,computers, simple telephones and enhanced telephones. FIGS. 26-28, forexample, depict a telephone with video capability that includes such amodem, a simple telephone that includes such a modem, and a socket fordata interface, a fax machine that includes such a modem and a computerthat includes such a modem. Like some of the currently available faxmachines, the computer may include all circuitry that is needed for thetelephone function, leaving only the hand set to be connected to theRJ-11 plug. Like the AT&T 7300 PC, hands free Speakerphone capabilitycan be incorporated. It may be noted that the modem shown in FIG. 28 isdepicted as a box but, more likely, it will be constructed on a printedcircuit board and plugged into one of the standard open slots that arein the computer. The RJ-11 connector that is depicted in the drawing andinto which a telephone on the telephone hand-set would be plugged in(depending on the design, as discussed above) might be on the modem'sprinted circuit board, or it might be positioned in the PC's housing foreasier access by the user.

Sketching Unit for Transmission of Notes Over Telephone

FIG. 31 is block diagram of the sketching unit of the present invention.In FIG. 31, telephone 700 transmits analog voice signals to signalcombiner/de-combiner 702 for combining the voice signal with digitalsignals output from sketch pad 704. The combined signal is thentransmitted over a standard telephone line via conventional telephoneswitch 706 to signal combiner/de-combiner 708 for separating thecombined signal into the voice analog signal and the sketch pad digitalsignals. Once the combined signal has been separated, the analog voicesignal is transmitted to telephone 712 to establish voice communicationbetween telephones 700 and 712. In addition, the digital signal istransmitted to sketch pad 710 to establish graphical communicationbetween sketch pads 704 and 710.

The above description for FIG. 31 was provided for voice and sketchcommunication generated by telephone 700 and sketch pad 704. However,this description is equally applicable when telephone 712 and sketch pad710 generate the voice and digital signals for transmission to telephone700 and sketch pad 704.

FIG. 32 is a more detailed block diagram of the sketching unit of thepresent invention. In FIG. 32, telephone 700 transmits analog voicesignals to signal combiner/de-combiner 702. In addition, digitizer 714transmits digital signals identifying x-y coordinate positions of pen 15to microprocessor 718. Microprocessor 718 transmits the digital signalsto signal combiner/de-combiner 702 which combines the analog voicesignal with the digital signal for transmission over a conventionaltelephone line.

Signal combiner/de-combiner 702 preferably comprises the signalcombiner/decombiner of the present invention as illustrated in FIGS. 6and 10 which is able to provide simultaneous use of sketch pad 704 andtelephone 700 over a single telephone line. However, signalcombiner/de-combiner 702 may also be any suitable device which is ableto combine digital and analog signals and separate a combined signalinto its digital and analog components. In addition, digitizer 714 ispreferably a clear digitizing pad which is placed on top of LCD screen716. Digitizer 714 and LCD screen 716 are conventional and may be, forexample, the combined clear digitizing pads and LCD screens manufacturedby Apple Computer Company for the NEWTON Computer, or the EXPERT PADmanufactured by Sharp Company. Further, digitizer 714 and LCD screen 716may be separate devices. For example, digitizer 714 may be the cleardigitizer manufactured by Touch Technology, and LCD screen 716 may be,for example, one of the family of LCD screens manufactured by Epson orSharp Company.

Microprocessor 718 processes the received signals from digitizer 714 andilluminates the appropriate pixels in LCD screen 716 so that the user ofpen 715 on digitizer 714 is able to view the image being created on LCDscreen 716. In addition, microprocessor 718 receives digital signalsgenerated by another sketch pad, e.g., sketch pad 710 in FIG. 31, fordisplay on LCD screen 716 as well. Thus, LCD screen 716 is illuminatedin response to a user of its own sketch pad 704 as well as inputs fromother sketch pads. Microprocessor 718, however, transmits the digitalsignal from sketch pad 704 and other sketch pads according to apre-defined user selective format as will be discussed in greater detailbelow. Microprocessor 718 is conventional and may be, for example, astandard 16 bit input/output micro processor available via Intel, etc.Alternatively, microprocessor 718 may also be a standard digital signalprocessor having a 16 bit input/output capability such as the AT&T DSP16A.

Microprocessor 718 is connected to standard memory 720 which mayinclude, for example, a random access memory (RAM) or a read only memory(ROM) for storing instructions for processing the digital data receivedfrom signal combiner/de-combiner 702 and digitizer 714 (the specificformat for transmitting the digital data will be discussed in greaterdetail below). However, the various instructions which microprocessor718 uses for transmitting the digital data may be, for example, writtenin microcode, and based upon the transmission format discussed below maybe provided to microprocessor 718 by any standard software/processorprogrammer or developer.

Microprocessor 718 may also transmit the digital data according to theuser selective format to printer expansion module 722 which formats thedigital data in a compatible format for an attached printer.Alternatively, printer expansion module 722 and the printer may becombined in an integrated device. In addition, a conventional auxiliarymemory 726 is provided for storing images that the user wishes to retainfor later use. Microprocessor 718 transmits the images to memory 726upon selection of the feature by the sketch pad user which is describedin greater detail below.

Finally, microprocessor 718, upon selection by a user, transmits thedigital data to facsimile expansion module 724 to format the digitaldata according to standard facsimile communication requirements fortransmission by a facsimile machine connected thereto. Alternatively,facsimile expansion module 724 and the facsimile machine may be combinedin an integrated device.

FIG. 33 is a diagram of the user interface of the sketching unit of thepresent invention which defines the user selective format and functionsfor microprocessor 718 to transmit digital data to signalcombiner/de-combiner 702 and to transmit digital data to the LCD screen716. As shown in FIG. 33, the user selective format preferably isdetermined from predesignated coordinates on digitizer 716 whichmicroprocessor 718 is pre-programmed to identify. Accordingly, whenmicroprocessor 718 received coordinates from, for example, thesend/don't send function 728 locations on digitizer 714, microprocessordetects the pre-designated coordinates according to conventionaltechniques and performs the appropriate function as is hereinafterdescribed.

The send/don't send function 728 is used to permit sketch pad 704 userto transmit the digital data while the image is being created ondigitizer 714 when the send/don't send function 728 is in the send mode,i.e., the pen user has touch portion 728 of digitizer 714 which reads"send". When the send/don't send function 728 is in the don't send mode,microprocessor 718 will collect the various coordinate data fromdigitizer 714 in memory 720 and hold transmission of all the digitaldata until the send/don't send function is placed in the send mode. Oncethe send/don't send function is placed in the send mode, microprocessor718 will transmit all the collected data to the destination sketch padfor graphical communication.

Next, digitizer 714 includes clear function 730 which clears the entireLCD screen 716 when clear function 730 is in the clr 1 mode, and alsoattempts to clear the LCD screen of another sketch unit when clearfunction 730 is in the clr 2 mode. As will be described, the LCD screenof the another sketch unit will be cleared when the user of the othersketch unit has placed the LCD screen in an unlock mode.

Digitizer 714 also includes write function 732 which indicates tomicroprocessor 718 to write data, i.e. illuminate, LCD screen 716 whenthe write function 732 is in the pen mode. When write function 732 is inthe erase mode, microprocessor 718 erases all coordinate data created bypen 715, and selectively does not illuminate LCD screen 716.Accordingly, the user is able to selectively erase portions of imagescreated by sketch unit 704 or even other sketch units.

Digitizer 714 further includes lock function 734 which indicates tomicroprocessor 718 to prevent digital data transmitted from othersketching pads from being transmitted to LCD screen 716 when lockfunction 734 is in the lock mode. Thus, the lock mode permits the userof sketch pad 704 from being interrupted by continuous transmission fromanother sketch pad such as by a non-stop image "talker". Lock function734 also includes the opn mode which opens LCD screen 716 to othersketch pad users and permits LCD screen 716 to be altered responsive toother sketch pads.

Finally, digitizer 714 includes a store function, sto 735, for storingimage data in auxiliary memory 726, a print function, prt 738, forprinting the image data on a printer via printer expansion module 722,and a facsimile function, fax 736, for transmitting the image data usinga facsimile machine via facsimile expansion module 724.

While the above functions have been described using digitizer 714 tonotify microprocessor 718 of the various selected functions, otherconventional means may be used such as simple toggle switches placed onthe sketching unit or on the auxiliary devices to indicate tomicroprocessor 718 of the selected function.

In addition, while the previous discussion assumed all portions of LCDscreen 716 were used by both sketch pad 704 and other sketch pads, LCDscreen may alternatively be divided into first and second sections. Thefirst section is preferably used for the pen user of sketch pad 704 tocreate images which are transmitted to another sketch pad, but ispreferably not used for receiving images from other sketch pads. Thesecond section is preferably used for receiving images from other sketchpads, but is typically not used for generating images to be transmittedto the other sketch pads. In this manner, sketch pad 704 is able toseparate out various images and permits concurrent image communicationof separate images. In order to accomplish this feature, microprocessor718 is pre-programmed according to conventional techniques to recognizethat certain coordinates of LCD screen 716 are illuminated responsive toother sketch pad digital data and other coordinates are illuminatedresponsive to digital signals generated pen 715 creating an image ondigitizer 714. This feature may also be user selectable in a similarmanner as the functions described with reference to FIG. 33.

For the divided screen feature, sketch pad 704 preferably includes acopy function which permits the sketch pad receiving the image on afirst part of LCD screen 716 and copied to a second part of LCD screen716 where the sketch pad user may alter the received image andre-transmit the altered image back to the sketch pad which created theinitial image. This feature may be implemented in a similar manner asthe previous features where a particular coordinate pair is designatedto indicate to microprocessor 718 to copy the same image which isdisplayed on one part of LCD screen 716 onto a second part of LCD screen716 using memory 720 which would store current images displayed on LCDscreen 716.

Further, sketching pad 704 may also be provided with the function ofautomatically establishing connection with an incoming telephone callwhen the telephone call is not answered and the person is not availableto answer the voice or graphical call. In this scenario, sketching pad704 is provided with a conventional call detection device whichdetermines that an incoming call is being received by the sketching padand a timer for determining when the incoming call has reached apredesignated time out period which indicates that no person isavailable to receive the telephone voice/graphic call. Accordingly,sketch pad 704 may then be actuated to receive the graphical data eventhough no person receives the telephone call. This provides the addedbenefit of, for example, being able to graphically communicate withanother party when the other party is not home. For example, traveldirections or written messages may be left on the other sketch pad andmay be used concurrently with the voice answering machine.

The many features and advantages of the invention are apparent from thedetailed specification, and thus, it is intended by the appended claimsto cover all such features and advantages of the invention which fallwithin the true spirit and scope of the invention. Further, sincenumerous modifications and variations will readily occur to thoseskilled in the art, it is not desired to limit the invention to theexact construction and operation illustrated and described, andaccordingly, all suitable modifications and equivalents may be resortedto, falling within the scope of the invention.

What is claimed is:
 1. A sketching system for sketching first notes to be transmitted over a telephone line during a telephone call using the telephone line, the sketching system receiving second notes from another sketching system, the sketching system comprising:a signal de-combiner device, receiving the second notes from the another sketching system and voice data as a combined signal via the telephone line and de-combining the combined signal into the second notes and the voice data, said signal de-combiner device includinga demodulator for receiving the combined signal and outputting a demodulated signal; detection means for receiving the demodulated signal from said demodulated and for detecting digital signal components included in the demodulated signal; a first de-mapper connected to said detection means and generating the first notes responsive to said digital signal components; subtraction means for subtracting the digital signal components received from said detection means and generating component analog signals; and a second de-mapper connected to said subtraction means and generating a voice signal responsive to the component analog signals; a sketching unit connected to said signal de-combiner device and includinga note displaying device displaying the first and second notes; a note generating device generating the first notes; a processor connected to said note displaying and generating devices and to said signal de-combiner device, receiving the first notes from said note generating device, receiving the second notes from said de-combiner device, and transmitting the first and second notes to said note displaying device, clearing means for clearing one of said note displaying device and another note displaying device of said another sketching system; erase means for selectively erasing the first and second notes displayed on one of said note displaying device and said another note displaying device; first lock means for preventing said processor from transmitting the first notes to said signal de-combiner device preventing the first notes from being displayed on said another sketching system; and second lock means for preventing said processor from transmitting the second notes to said note displaying device.
 2. A method of sketching first notes using a sketching system to be transmitted over a telephone line during a telephone call using the telephone line, and receiving second notes from another sketching system, the method comprising the steps of:(a) receiving the second notes from the another sketching system and voice data as a combined signal via the telephone line and de-combining the combined signal into the second notes and the voice data, said receiving step (a) further comprising the steps of(a1) demodulating the combined signal and outputting a demodulated signal; (a2) detecting digital signal components included in the demodulated signal; (a3) generating the first notes responsive to said digital signal components using a first de-mapper; (a4) subtracting the digital signal components detected in said detecting step (a2) and generating component analog signals; and (a5) generating a voice signal responsive to the component analog signal using a second de-mapper; (b) generating the first notes; (c) displaying the first notes generated in said generating step (b) and displaying the second notes received in said receiving step (a); (d) selectively clearing one of a note displaying device of the sketching system and another note displaying device of another sketching system; (e) selectively erasing the first and second notes displayed on the one of the note displaying device of the sketching system and the another note displaying device of the another sketching system; (f) selectively preventing transmission of the first notes to the another sketching system; and (g) selectively preventing transmission of the second notes to the note displaying device of the sketching system. 